London (CNN)– Olympic judo competitor Hemeed Al Drie plans to sin during the Games in London, he admits with a grin.

"God is merciful and compassionate, even when our sins are many," said Al Drie, kneeling on a mat while martial artists hurled each other to the floor around him.

Al Drie's sin isn't what you might expect. It's that he is planning to eat and drink while the sun is up during the Olympics, even thought the Games fall smack in the middle of the Muslim holy month of Ramadan.

Observant Muslims are supposed to fast during Ramadan, abstaining from all food and drink, even water, during daylight hours, then eating and drinking after sundown. Fasting for the month is a major religious obligation, one of the Five Pillars of Islam.

But Al Drie, 19, knows that fasting on days when he has up to six judo matches against the world's best competitors would doom his chances of winning.

"If you don't eat and you enter a competition, you might faint," he said. That would lead to instant elimination.

So Al Drie is going to stick to his normal competition diet.

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"Maybe some people will fast, and that's good for them. But for me, I can't risk losing any of my matches," he said.

Al Drie, who is from the United Arab Emirates, isn't alone in facing the Ramadan dilemma. It's not clear exactly how many Muslim athletes are competing in the Olympics this year, but more than one in five people around the world - about 23% - is Muslim, according to estimates by the Pew Forum on Religion & Public Life.

Religious experts in Saudi Arabia determine the starting date of Ramadan each year based on the phase of the moon.

Muslim athletes face a particular challenge because there are so many hours of daylight in London during the Games, says sports nutritionist Hala Barghout.

"It's a 17-hour fast in London. It's not like here in the Middle East," said Barghout, from the United Arab Emirates.

It is "physically impossible" for a world-class athlete to stuff as much food as they need into their body during the seven hours of darkness that remain, she said.

"How much can a person eat in one meal? You can't have, say, 3,000 or 4,000 calories in one meal. You need time to digest," she said. Three thousand calories is the amount that the U.S. government recommends that an active man in his 20s eat in an entire day.

Explain it to me: Ramadan

But one of the leading Islamic religious leaders in the Middle East says Muslims competing in the Olympics should observe the daytime fast, regardless of how it affects their performance.

"Playing sports is not a requirement in Islam. Players become athletes by choice. This optional activity, therefore, does not allow athletes to break their fast," said Ahmed Abdul Aziz Al Haddad, the grand mufti of Dubai.

Muslim athletes must also observe the fast because they are representing Islam at the Olympics, Al Haddad said.

"They must be ambassadors of their faith," he said. "Meaning that Islam must be present in their actions, and they do not fall into anything that Islam forbids."

Competitors may eat or drink if fasting is threatening their health, he said."If a person feels extreme fatigue, sharia allows him to break his fast. Sharia is flexible," he said, using the Arabic word for Islamic law.

"But to immediately break your fast without being hungry or thirsty is the same as submitting to your cravings and lusts, and not putting God's desire before your own," the religious scholar argued.

Not all Muslim authorities agree with Al Haddad.

British Olympic rower Moe - for Mohamed - Sbihi has discussed the problem with his imam, and decided not to fast during the Games.

He plans to feed 1,800 hungry people in Morocco after the Games as compensation for not fasting during the holy month, and will observe a fast later.

"It was a hard decision for me to make," said Sbihi, who was born in Britain to an English mother and Moroccan father.

"When I first started rowing as a youngster, I said that I'd be fasting regardless," he said.

But over time he changed his mind. He did his university dissertation on fasting in sports, and consulted family, friends and coaches in Morocco and Britain before making his decision, he said.

British rower Mohamed 'Mo' Sbihi.

"In the end it felt like I was making the right decision for me, and that's to postpone my fast, to make it up at a later date," he said.

Sbihi has been considering the Ramadan dilemma for years, since it became clear that the 2012 Games would fall during the holy month. They usually don't. The Muslim calendar follows the moon, so Ramadan falls during different seasons in different years.

Members of the London committee organizing the Games this year noted it was not their decision to hold them during Ramadan - the International Olympic Committee sets the date.

The IOC pointed out that the Games "bring together virtually every religion and creed. ... How to deal with religious practices is up to each athlete and his/her personal beliefs."

Sandrine Tonge, a spokeswoman for the IOC, said different countries and individuals deal with the question differently.

"Some countries, like Egypt, for example, issue fatwas exempting athletes from the need to fast when competing," she said, using the Arabic word for a Muslim religious ruling. "At the end, religious practice is a matter for individual conscience."

The London organizers pointed out that major international sports events have taken place during Ramadan before, including the Singapore Youth Olympic Games in 2010.

Dining facilities in the Olympic Village will be open 24 hours a day, and athletes observing Ramadan will be able to order "break-of-fast packs that will include water, nutritional bars and fruit," the organizing committee says.

Even with those provisions in place, and with the Games beginning in just days, Khadijah Fahed Mohammed hasn't decided whether she will fast.

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The 17-year-old weightlifter is the first woman from the United Arab Emirates ever to qualify for the Games.

Her nutritionist has put together a plan for her to consume 5,000 calories a day - more than twice as much as an active woman her age should normally eat, according the U.S. guidelines.

She's torn between her obligation to fast and her desire to win.

"Both are important to me. Fasting is a must," she said, even as she recognizes the importance of her first time in the Olympics.

"This is our chance. Ramadan just happened to be at the same time as the competition, so no one knows what to do. Should we fast or not?" she asked.

Her coach says she should.

"Many competitions have taken place during Ramadan," said Nagwan El-Zawawi. "I am not convinced you can break your fast. I mean, fasting is a must. There are no excuses."

But judo competitor Al Drie doesn't believe that.

"God is with me wherever I go, whether I fast or not," he insisted. "The most important thing is to have faith in God and give it your best and thank God, whether you win or lose."

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